The hydrological response of Northeastern Brazil during \ud last deglaciation

Abstract

Paleociimate proxy and numerical modelling data suggest prominent change in precipitation over lowland tropical South America during last deglaciation. The hydrography of Northeastem Brazil under such change in precipitation, however, remains poorly investigated. Unresolved issues relate to the possible change in sources and amounls of terrigenous input delivered to the continental slope off Northeastern Brazil. Here we analyzed a set of marine sediment cores retrieved from off the Parnaíba River Delta during research cruise MSM20/3 that provide an excellent opportunity to \ud address these issues. Detailed radiocarbon-based age models indicate that the sedimentation rates at our core sites increased significantly from ~ 20 cm/kyr during the Last Glacial Maximum to ~70 cm/kyr during Heinrich Stadial1, and then back to ~ 20 cm/kyr during the Bolling-Allerod. One possibility for this extreme rise in sedimentation rate is the simulated reversal of the North Brazil Current and lhe supposed input of Amazonian sediment to the continental slope off the Parnaiba River Delta. Here \ud our Nd isotopic data will help to disentangle the different sedimentary sources since the terrigenous supply from the Parnaíba and the Amazon Rivers have considerably different signatures. The ENd(O) measurement of modern sediment samples (i.e., soil, river suspended sediment load), to be collecled over Northeastem Brazil and already available marine surface and downcore results will greatly contribute to clarify possible change in the terrigenous sources. Our data shed new light into our knowledge of the coupled hydrological process (i.e., fluvial erosion and weathering) over Northeastem \ud Brazil and its relationship with the Atlantic Meridional Oceanic Circulatio